FIG. 4.
Effect of Δyfu and Δyiu mutations on iron-deficient or iron-chelated growth of Y. pestis strains in a Ybt− Yfe− background. Y. pestis strains were grown in deferrated PMH2 medium without (A) or with (B) 45 μM DIP at 37°C. The following strains were used: Yfe−, KIM6-2031.1; Yfe− Yfu−, KIM6-2082.1; Yfe− Yfu− Yiu−, KIM6-2123.2. An essential condition for demonstrating a differential growth effect by the yfu and yiu mutants was a low initial inoculum (OD620 of 0.005). The growth curves shown represent one of two independent experiments that yielded similar results.